The present invention relates to a new assembly for packaging a high power dimmable LED light source that can be further incorporated into a larger lighting assembly. More specifically, this invention relates to a replaceable lighting head assembly comprised of a high output LED socket torch, a vertically aligned thermal heat sink and an electrical connector. In itself, this section acts as an electrical inter-connect as well as a thermal heat sink interface suitable for small package integration. The secondary housing unit of this assembly provides a thermal pathway for the heat received from the heat sink to the external environment and acts as a conduit for easy access to the external electrical source. If desired, it can also act as a base for further fixture design functions. This assembly, when integrated into the design of a light housing, provides a means by which to manipulate the light beam of the lighting fixture.
The evolution of electric lighting began in the late 1800's with the first incandescent bulb—essentially a “glowing wire in a bottle”. In spite of all the improvements, the light bulb that we use today is really not much different than the one invented by Thomas Edison. Inherent problems such as premature failures due to delicate glass structure or filaments, environmental concerns with the mercury, lead or toxic and flammable gases used, and intrinsic inefficiencies are still a concern. Less than 10% of the energy required to burn an incandescent light bulb is converted to light. Even flourescent lighting—today's most efficient light source, converts only 30–40% into light. Although not yet at the levels of flourescent lighting, LED's have the potential to convert up to 90% of the energy they receive into light. Further, light from conventional sources is emitted in all directions, requiring the use of optics to re-direct the beam in the desired direction for effective illumination. Each time the light is redirected, fixture efficiency decreases. The light generated by an LED, however, is directional so its efficiency doesn't have to necessarily match other light sources to be more effective.
Much of the energy a standard filament light source consumes is converted into hot infrared rays that radiate out within the light beam, thus requiring extra caution when handling the bulb. Because of the heat generated, restrictions to the type and size of the casing around these bulbs must be maintained—all of which reduce the flexibility of the lighting system.
Since the human eye is naturally drawn to the brightest source of illumination, flexibility is often required in the distribution of the light. General and accent lighting applications utilize this premise to direct the attention of the viewer to particular areas or items. If the first thing a viewer sees is the harsh light source, then their first impression may be negative. The increased size of the bulb casing results in a larger area from which the light emanates, thus requiring greater attention to positioning of the fixture to avoid direct eye contact with the light source itself.
This flexibility is sometimes related to the light being used in a space that has changing requirements. An example is a retail space where different products are displayed in different ways each week. In this example, spot lights may be desirable for small items and wider beam lights may be appropriate for larger items. The option available today is to use fixtures with integral reflectors that have different beam spreads. One example of this is low-voltage halogen lamps, of which MR-16 is a common type. The MR-16's are available in several light beam spreads from very narrow spot to very wide flood. This strategy causes complications when lamps are changed after burning out. All MR-16's are very similar in appearance, and beam patterns within a space are only maintained after re-lamping if the exact same lamp is used to replace the burned out lamp. This strategy also requires many different lamp types to be kept on hand.
In outdoor lighting, a fixture should be flexible enough to allow landscape or architectural features to be highlighted as elements change, such as when trees or bushes grow—as well as being discrete enough as to not draw the attention of the eye. If not, the resulting brightness one sees actually makes it harder to observe the surrounding environment as it causes everything else to appear darker. Further, traditional light sources have a relatively short life span, necessitating bulb replacement. This can be both time consuming and dangerous if such fixtures are mounted in an elevated position such as on the soffit of a building or high in a tree.
Contrast to that, LED light sources offer small, directional pinpoints of light. Their size and directionality support highly controllable lighting systems capable of delivering high flux output at relatively low current levels for long periods of time. But in order to achieve this, thermal issues associated with high output LED lighting systems must be addressed. The challenge is to conduct the heat generated within the LED onto the fixture and then to dissipate that heat, via convection, to the surrounding ambient air. Proper design, therefore, must be given to the sizing of the heat sink to create both a pleasing aesthetic look and functional heat dissipation.
It would thus be desirable to provide a lighting assembly contained within a small footprint that can be incorporated into various fixture designs. It would be further advantageous if that lighting assembly allows for easy adjustment of the light beam spread in addition to allowing for changes in light intensity through the use of collimating lenses—without having to change the bulb. It would be of further benefit if such assembly were to include a state-of-the-art high output LED for its long life, reduced maintenance cost and reduced cost of ownership—that is replaceable so that when advances in the industry become available the light source can be updated by the consumer.
High output LED light sources are increasingly becoming the choice of illumination. These dimmable solid-state devices have no filament to break or glass to shatter, no mercury, toxic gases or lead to contaminate the environment and no infrared or UV in the light beam. They are fast approaching the efficiency of fluorescent light sources with new performance standards being achieved regularly.
High output LED's differ from conventional LED light sources in that they are able to separate their thermal and electrical pathways. This enables them to draw more heat away from the emitter core and thus significantly reduce thermal resistance. As a result, high output LED's can handle significantly more power than conventional LED's. However, the higher electrical input also means they tend to operate at higher operating temperatures which can degrade their performance. Heat that is not effectively dissipated can shift colors, reduce brightness and significantly shorten their life span.
Moreover, most heat sink configurations currently available are directed to a planar circuit board mount with a heat spreader or a horizontal finned heat sink design. Neither of these arrangements is suitable for small vertical package integration or compact lighting head construction.